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Loops
Budditha Hettige
Department of Computer Science
IT 1033: Fundamentals of Programming
Repetitions: Loops
• A loop is a sequence of instruction s that is
continually repeated until a certain condition is
reached.
• The statement may be repeated
– For a specific number of items
– For an indeterminate number of times, depending
on the truth or falsity of some condition.
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Loops
• C++ provides three types of loops
– for loops (1- n times)
• Repeat a section of code known number of times
– while loops (0 – more times)
• Loop is used to repeat a specific block of code an unknown number of times
– do while loops (1 – more times)
• A do while loop is a control flow statement that executes a block of code at least once, and then repeatedly executes the block
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Repeat some work
• Do some repeated work
– Initialization (Start number)
– Condition (do repeat action until satisfy some condition)
– Update (Next Value)
• Example
– Initialization Start with 1
– Condition Count up to 50
– Update Count 1 by 1
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For Loop• Syntax
for (initialization; condition; update)
{
statement(s)
}
• Example
Initialization
Update
Condition
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Exercise 6.1
Write a C++ program to find
the factorial of a given
number
Example:
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Answer
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Nested for Loops
• A loop can be nested inside of another loop. C++ allows at least 256 levels of nesting.
• Syntaxfor ( init; condition; increment )
{
for ( init; condition; increment )
{
statement(s);
}
statement(s);
}
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Exercise 6.2
• Write a C++ program to display the following
Multiplication table
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Exercise 6.3
1. Write a c++ program to print the
following figure
a) * b) 1
** 12
*** 123
**** 1234
***** 12345
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While Loop
• Allows the repetition of a statement based on the
truth value of a condition
• Can run 0 to infinite times
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While Loop
• Syntax
while (Condition)
{
statement(s)
}
• ExampleInitialization
Update
Condition
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Exercise 6.4
• Write a C++ program
to accept numbers
until the user enters a
999 and output the
sum of the given
numbers
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Exercise 6.5
Create a java program to identify the given number is Palindrome number or not.
– Read number as an integer
– Find the number is Palindrome or not
– Print the results
Hint:A palindromic number or numeral palindrome is a number that remains the same when its digits are reversed. Like 16461
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Answers
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Do-while Loop
• do…while loop also depends on a condition, but
unlike while loop, its condition is evaluated at the
bottom of the loop, after the body has already
executed.
Budditha Hettige ([email protected])
Do-while Loop
• Syntaxdo
{
statement(s)
}
while (condition);
Example Initialization
Update
ConditionBudditha Hettige ([email protected])
Loops comparison
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Exercise 6.6
Accept numbers until the
user enters a 999 and
output the average of the
given numbers
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Exercise 6.7
• Using do-while loop, create a java program to
display the selected option in the following menu;
[1] Enter data
[2] Print data
[3] Exit the program
do-while
Switch
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Answer
Budditha Hettige ([email protected])
Exercise 6.8
Write a C++ program to read N number of integers and
find the total and average.
• N is an input 1, 2, 3….. N
• Use for, while and do-while loops
• Draw 3 flow chart for the above 3 programs
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Exercise 6.9
Write a C++ program to compute the gross pay for an
employee. An employee is paid at hourly rate for the
first 40 hours worked in a week. Any hours worked in
excess of 40 hours are paid at the overtime rate of one
and half times that. Your program should print the pay
sheets of all the employees.
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